Organic electroluminescent materials and devices

ABSTRACT

A compound having a structure according to formula (I) 
     
       
         
         
             
             
         
       
     
     is disclosed. In formula (I), Cu is a monovalent copper atom; *C is a carbene carbon; X 1  and X 2  are selected from alkyl, cycloalkyl, alkoxy, amino, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, heteroalkynyl, arylalkyl, aryloxy, aryl, heteroalkyl, heteroaryl, and combinations thereof; X 1  is bonded to *C by a C atom, and X 2  is bonded to *C by an N atom; X 1  and X 2  are optionally joined to form a ring; and Y is selected halide, alkyl, cycloalkyl, alkoxy, amino, phosphine, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, heteroalkynyl, arylalkyl, aryloxy, aryl, heteroalkyl, heteroaryl, and combinations thereof. A formulation containing compound having a structure according to formula (I), and a device with an organic layer comprising disposed between an anode and a cathode, that includes a compound having a structure according to formula (I) are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/478,838, filed Sep. 5, 2014, which claims priority to U.S.Application Ser. No. 61/894,611, filed Oct. 23, 2013, the entirecontents of which are incorporated herein by reference.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to compounds for use as emitters anddevices, such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)3, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

According to an embodiment, a compound comprising the structure offormula (I)

is provided. In the structure of formula (I):

Cu is a monovalent copper atom;

*C is a carbene carbon,

X₁ and X₂ are selected from the group consisting of alkyl, cycloalkyl,alkoxy, amino, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,heteroalkynyl, arylalkyl, aryloxy, aryl, heteroalkyl, heteroaryl, andcombinations thereof;

X₁ and X₂ are bonded to *C by an atom independently selected from thegroup consisting of C, N, O, S, and P,

X₁ and X₂ are optionally joined to form a ring, and

Y is selected from the group consisting of halide, alkyl, cycloalkyl,alkoxy, amino, phosphine, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,heteroalkynyl, arylalkyl, aryloxy, aryl, heteroalkyl, heteroaryl, andcombinations thereof.

According to another embodiment, a first device comprising a firstorganic light emitting device is also provided. The first organic lightemitting device can include an anode, a cathode, and an organic layer,disposed between the anode and the cathode. The organic layer caninclude a compound of formula (I). The first device can be a consumerproduct, an organic light-emitting device, and/or a lighting panel.

Formulations containing a compound of formula (I) are also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows Formula (I) as disclosed herein

FIG. 4 is a graph of normalized intensity (a.u.) versus wavelength forseveral compounds of interest.

FIG. 5 is a is a graph of normalized intensity (a.u.) versus wavelengthfor several compounds of interest.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention maybe incorporated into a wide variety of consumer products, including flatpanel displays, computer monitors, medical monitors, televisions,billboards, lights for interior or exterior illumination and/orsignaling, heads up displays, fully transparent displays, flexibledisplays, laser printers, telephones, cell phones, personal digitalassistants (PDAs), laptop computers, digital cameras, camcorders,viewfinders, micro-displays, 3-D displays, vehicles, a large area wall,theater or stadium screen, or a sign. Various control mechanisms may beused to control devices fabricated in accordance with the presentinvention, including passive matrix and active matrix. Many of thedevices are intended for use in a temperature range comfortable tohumans, such as 18 degrees C. to 30 degrees C., and more preferably atroom temperature (20-25 degrees C.), but could be used outside thistemperature range, for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The term “halo” or “halogen” as used herein includes fluorine, chlorine,bromine, and iodine.

The term “alkyl” as used herein contemplates both straight and branchedchain alkyl radicals. Preferred alkyl groups are those containing fromone to fifteen carbon atoms and includes methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tert-butyl, and the like. Additionally, thealkyl group may be optionally substituted.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals.Preferred cycloalkyl groups are those containing 3 to 7 carbon atoms andincludes cyclopropyl, cyclopentyl, cyclohexyl, and the like.Additionally, the cycloalkyl group may be optionally substituted.

The term “alkenyl” as used herein contemplates both straight andbranched chain alkene radicals. Preferred alkenyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkenyl groupmay be optionally substituted.

The term “alkynyl” as used herein contemplates both straight andbranched chain alkyne radicals. Preferred alkynyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkynyl groupmay be optionally substituted.

The terms “aralkyl” or “arylalkyl” as used herein are usedinterchangeably and contemplate an alkyl group that has as a substituentan aromatic group. Additionally, the aralkyl group may be optionallysubstituted.

The term “heterocyclic group” as used herein contemplates aromatic andnon-aromatic cyclic radicals. Hetero-aromatic cyclic radicals also meansheteroaryl. Preferred hetero-non-aromatic cyclic groups are thosecontaining 3 or 7 ring atoms which includes at least one hetero atom,and includes cyclic amines such as morpholino, piperdino, pyrrolidino,and the like, and cyclic ethers, such as tetrahydrofuran,tetrahydropyran, and the like. Additionally, the heterocyclic group maybe optionally substituted.

The term “aryl” or “aromatic group” as used herein contemplatessingle-ring groups and polycyclic ring systems. The polycyclic rings mayhave two or more rings in which two carbons are common to two adjoiningrings (the rings are “fused”) wherein at least one of the rings isaromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl,heterocycles, and/or heteroaryls. Additionally, the aryl group may beoptionally substituted.

The term “heteroaryl” as used herein contemplates single-ringhetero-aromatic groups that may include from one to three heteroatoms,for example, pyrrole, furan, thiophene, imidazole, oxazole, thiazole,triazole, pyrazole, pyridine, pyrazine and pyrimidine, and the like. Theterm heteroaryl also includes polycyclic hetero-aromatic systems havingtwo or more rings in which two atoms are common to two adjoining rings(the rings are “fused”) wherein at least one of the rings is aheteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls,aryl, heterocycles, and/or heteroaryls. Additionally, the heteroarylgroup may be optionally substituted.

The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group,aryl, and heteroaryl may be optionally substituted with one or moresubstituents selected from the group consisting of hydrogen, deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

As used herein, “substituted” indicates that a substituent other than His bonded to the relevant position, such as carbon. Thus, for example,where R¹ is mono-substituted, then one R¹ must be other than H.Similarly, where R¹ is di-substituted, then two of R¹ must be other thanH. Similarly, where R¹ is unsubstituted, R¹ is hydrogen for allavailable positions.

The “aza” designation in the fragments described herein, i.e.aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more ofthe C—H groups in the respective fragment can be replaced by a nitrogenatom, for example, and without any limitation, azatriphenyleneencompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. Oneof ordinary skill in the art can readily envision other nitrogen analogsof the aza-derivatives described above, and all such analogs areintended to be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described asbeing a substituent or otherwise attached to another moiety, its namemay be written as if it were a fragment (e.g. phenyl, phenylene,naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g.benzene, naphthalene, dibenzofuran). As used herein, these differentways of designating a substituent or attached fragment are considered tobe equivalent.

According to one embodiment, a compound comprising the structure offormula (I)

is described. In the structure of formula (I):

Cu is a monovalent copper atom;

*C is a carbene carbon,

X₁ and X₂ are selected from the group consisting of alkyl, cycloalkyl,alkoxy, amino, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,heteroalkynyl, arylalkyl, aryloxy, aryl, heteroalkyl, heteroaryl, andcombinations thereof;

X₁ and X₂ are bonded to *C by an atom independently selected from thegroup consisting of C, N, O, S, and P,

X₁ and X₂ are optionally joined to form a ring, and

Y is selected from the group consisting of halide, alkyl, cycloalkyl,alkoxy, amino, phosphine, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,heteroalkynyl, arylalkyl, aryloxy, aryl, heteroalkyl, heteroaryl, andcombinations thereof.

In some embodiments, the compound can be an emissive dopant. In someembodiments, the compound can produce emissions via phosphorescence,fluorescence, thermally activated delayed fluorescence, i.e., TADF (alsoreferred to as E-type delayed fluorescence), triplet-tripletannihilation, or combinations of these processes.

In some embodiments, Y includes a carbene carbon, and the carbene carbonis coordinated to the Cu atom. In other embodiments, Y is coordinated tothe Cu atom by an atom that is not a carbene carbon.

In some embodiments, X₁ and X₂ are not joined. In some embodiments, X₁and X₂ are joined to form a ring A. In some embodiment ring A is a 5- or6-membered ring.

In some embodiments, ring A is part of a polycyclic ring system, whichmay be heterocyclic or carbocyclic. In some embodiments, ring A isnon-aryl. In some embodiments, ring A can be heterocyclic, while ring Acan be carbocyclic in other embodiments. In some embodiments, ring A canbe substituted by at least one substituent selected from the groupconsisting of alkyl, cycloalkyl, alkoxy, amino, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, heteroalkynyl, arylalkyl, aryloxy, aryl,heteroalkyl, heteroaryl, and combinations thereof.

In some embodiments, Y is amino and Cu—Y is, or comprises, a structureselected from the group consisting of:

where R is selected from the group consisting of hydrogen, alkyl,cycloalkyl, alkoxy, amino, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, heteroalkynyl, arylalkyl, aryloxy, aryl, heteroalkyl,heteroaryl, and combinations thereof.

In some embodiments, Cu—Y is, or comprises, a structure selected fromthe group consisting of:

wherein R₁, R₂, and R₃ are independently selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, alkoxy, amino, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, heteroalkynyl, arylalkyl, aryloxy,aryl, heteroalkyl, heteroaryl, and combinations thereof.

In some embodiments, the carbene structure

of formula (I) is, or comprises, a structure selected from the groupconsisting of:

wherein each n is independently 1 or 2,

wherein z is 1, 2, or 3;

wherein Y¹ is an atom selected from the group consisting of C, O, S, andN, and

wherein R, R₁, R₂, and R₃ are each independently selected from the groupconsisting of hydrogen, alkyl, cycloalkyl, alkoxy, amino, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, heteroalkynyl, arylalkyl, aryloxy,aryl, heteroalkyl, heteroaryl, and combinations thereof.

In some embodiments, Y in formula (I) is, or comprises, a structureselected from the group consisting of:

wherein each n is independently 1 or 2,

wherein z is 1, 2, or 3;

wherein Y² is an atom selected from the group consisting of C, O, S, andN, and wherein R, R₁, R₂, and R₃ are each independently selected fromthe group consisting of hydrogen, alkyl, cycloalkyl, alkoxy, amino,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, heteroalkynyl, arylalkyl,aryloxy, aryl, heteroalkyl, heteroaryl, and combinations thereof.

In some embodiments, the compound is selected from the group consistingof:

According to another aspect of the present disclosure, a first device isalso provided. The first device includes a first organic light emittingdevice, that includes an anode, a cathode, and an organic layer disposedbetween the anode and the cathode. The organic layer may include a hostand a phosphorescent dopant. The organic layer can be an emissive layer,which can include a compound according to Formula I, and its variationsas described herein.

The first device can be one or more of a consumer product, an organiclight-emitting device and a lighting panel. The organic layer can be anemissive layer and the compound can be an emissive dopant in someembodiments, while the compound can be a non-emissive dopant in otherembodiments.

The organic layer can also include a host. In some embodiments, the hostcan include a metal complex. The host can be a triphenylene containingbenzo-fused thiophene or benzo-fused furan. Any substituent in the hostcan be an unfused substituent independently selected from the groupconsisting of C_(n)H_(2n+1), OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n−1))₂,N(Ar₁)(Ar₂), CH═CH—C_(n)H_(2n+1), C≡C—C_(n)H_(2n+1), Ar₁, Ar₁—Ar₂, andC_(n)H_(2n)—Ar₁, or no substitution. In the preceding substituents n canrange from 1 to 10; and An and Are can be independently selected fromthe group consisting of benzene, biphenyl, naphthalene, triphenylene,carbazole, and heteroaromatic analogs thereof.

The host can be a compound comprising at least one chemical groupselected from the group consisting of triphenylene, carbazole,dibenzothiphene, dibenzofuran, dibenzoselenophene, azacarbazole,aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene. Thehost can include a metal complex. The host can be a specific compoundselected from the group consisting of:

and combinations thereof.

In yet another aspect of the present disclosure, a formulation thatcomprises a compound according to Formula I, and its variants asdescribed herein, is described. The formulation can include one or morecomponents selected from the group consisting of a solvent, a host, ahole injection material, hole transport material, and an electrontransport layer material, disclosed herein.

Combination With Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but not limit to: aphthalocyanine or porphyrin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and across-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, butnot limit to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, azulene; group consisting aromaticheterocyclic compounds such as dibenzothiophene, dibenzofuran,dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene,benzoselenophene, carbazole, indolocarbazole, pyridylindole,pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole,oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine,pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine,indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole,benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline,quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine,phenazine, phenothiazine, phenoxazine, benzofuropyridine,furodipyridine, benzothienopyridine, thienodipyridine,benzoselenophenopyridine, and selenophenodipyridine; and groupconsisting 2 to 10 cyclic structural units which are groups of the sametype or different types selected from the aromatic hydrocarbon cyclicgroup and the aromatic heterocyclic group and are bonded to each otherdirectly or via at least one of oxygen atom, nitrogen atom, sulfur atom,silicon atom, phosphorus atom, boron atom, chain structural unit and thealiphatic cyclic group. Wherein each Ar is further substituted by asubstituent selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH)or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but not limit tothe following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40;(Y¹⁰¹—Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹—Y¹⁰²) is a 2-phenylpyridine derivative. In anotheraspect, (Y¹⁰¹—Y¹⁰²) is a carbene ligand. In another aspect, Met isselected from Ir, Pt, Os, and Zn. In a further aspect, the metal complexhas a smallest oxidation potential in solution vs. Fc⁻/Fc couple lessthan about 0.6 V.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. While the Table below categorizes host materials as preferredfor devices that emit various colors, any host material may be used withany dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

wherein Met is a metal; (Y¹⁰³—Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴are independently selected from C, N, O, P, and S; L¹⁰¹ is an anotherligand; k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms Oand N.

In another aspect, Met is selected from Ir and Pt. In a further aspect,(Y¹⁰³—Y¹⁰⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting of aromatic hydrocarbon cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; thegroup consisting of aromatic heterocyclic compounds such asdibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene,benzofuran, benzothiophene, benzoselenophene, carbazole,indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole,triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole,thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine,oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole,indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline,isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine,phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine,phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Wherein each groupis further substituted by a substituent selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof.

In one aspect, host compound contains at least one of the followinggroups in the molecule:

wherein R¹⁰¹ to R¹⁰⁷ is independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, when it is aryl or heteroaryl, ithas the similar definition as Ar's mentioned above. k is an integer from0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X¹⁰¹ to X¹⁰⁸ isselected from C (including CH) or N.

Z¹⁰¹ and Z¹⁰² is selected from NR¹⁰¹, O, or S.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies as compared to a similar device lacking a blocking layer.Also, a blocking layer may be used to confine emission to a desiredregion of an OLED.

In one aspect, compound used in HBL contains the same molecule or thesame functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ isan integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy,aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, when it is aryl or heteroaryl, it has the similar definition asAr's mentioned above. Ar¹ to Ar³ has the similar definition as Ar'smentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selectedfrom C (including CH) or N.

In another aspect, the metal complexes used in ETL contains, but notlimit to the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinatedto atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer valuefrom 1 to the maximum number of ligands that may be attached to themetal.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated,and fully deuterated versions thereof. Similarly, classes ofsubstituents such as, without limitation, alkyl, aryl, cycloalkyl,heteroaryl, etc. also encompass undeuterated, partially deuterated, andfully deuterated versions thereof.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exiton/hole blocking layer materials,electron transporting and electron injecting materials may be used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table Abelow. Table A lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

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INORG. CHEM., DOI: 10.1021/ ic500889s (Jul. 23, 2014)

Experimental Synthesis of Compound 1 Step 1: Synthesis of1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-3-ium chloride

1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-3-ium chloride wassynthesized following published procedure (Chianese et al.,Organometallics, 2009, 28(2), 465-472.)

Step 2: Synthesis of1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-3-ium tetrafluoroborate

1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-3-ium chloride (440 mg,1.21 mmol) was mixed with ammonium tetrafluoroborate (127 mg, 1.21 mmol)in 30 ml of water and stirred at room temperature for 6 h. The whiteproduct was collected by filtration, washed with water, and dried invacuo (325 mg, 65%). NMR results confirmed the presence of1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-3-ium tetrafluoroborate:¹H NMR (500 MHz, acetone-d₆, δ) 2.48 (s, 12H), 7.42 (s, 2H), 7.62 (s,4H), 7.85 (m, 2H), 8.04 (m, 2H), 10.15 (s, 1H). ¹⁹F NMR (470 MHz,acetone-d₆, δ) −151.55.

Step 3: Synthesis of Compound 1: (BzI-3,5Me)₂Cu⁺

1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-3-ium tetrafluoroborate(282 mg, 0.68 mmol) from step 2, NaOtBu (84.9 mg, 0.884 mmol),[Cu(CH₃CN)₄]PF₆ (126.7 mg, 0.34 mmol), and 15 ml of anhydroustetrahydrofuran (THF) were mixed in 50 ml flask under N₂ atmosphere andstirred at room temperature overnight. The reaction mixture was filteredthrough Celite®. Following the addition of pentane, the product wasprecipitated from a dark yellow solution and the off-white solid wascollected by filtration. The product was further purified byrecrystalization from a THF/pentane mixture (114 mg). NMR resultsconfirmed the presence of compound 1: ¹H NMR (500 MHz, acetone-d₆, δ)2.35 (s, 24H), 7.17 (s, 4H), 7.34 (s, 8H), 7.54 (m, 4H), 7.68 (m, 4H).¹⁹F NMR (470 MHz, acetone-d₆, δ) −73.44, −71.94. ³¹P NMR (202 MHz,acetone-d₆, δ) −144.25.

Synthesis of Compound 2 Step 1: Synthesis ofN²,N³-bis(3,5-dimethylphenyl)pyrazine-2,3-diamine

2,3-Dichloropyrazine (5.58 g, 0.037 mol) and 3,5-dimethylaniline (11.21g, 0.0925 mol) were heated neat at 140° C. overnight under nitrogenatmosphere. The resulting solid was suspended in 200 ml of water and themixture was made strongly alkaline (pH=14) with a 25 wt-% aqueoussolution of NaOH. The mixture was extracted three times with 75 ml ofCH₂Cl₂ and three times with 75 ml of ethyl acetate. The combined organiclayers were dried with Na₂SO₄ and volatiles were removed by rotaryevaporation to give a brown oily residue. The addition of pentaneafforded a off-white solid, which was filtered, washed with pentane anddried to yield the desired product (7.145 g, 60%). NMR results confirmedthe presence of N²,N³-bis(3,5-dimethylphenyl)pyrazine-2,3-diamine: ¹HNMR (400 MHz, CDCl₃, δ) 2.29 (s, 12H), 6.18 (br s, 2H), 6.70 (s, 2H),6.88 (s, 4H), 7.77 (s, 2H).

Step 2: Synthesis of1,3-bis(3,5-dimethylphenyl)-2-ethoxy-2,3-dihydro-1H-imidazo[4,5-b]pyrazine

The N²,N³-bis(3,5-dimethylphenyl)pyrazine-2,3-diamine (750 mg, 2.35mmol) of step 1 was mixed with 10 ml of triethylorthoformate, followedby 0.193 ml of HCl_(conc). The mixture was stirred overnight in a closedvessel at 110° C. Upon cooling to 0° C. and the addition of pentane, theproduct was precipitated from a dark yellow solution. The beige solidwas collected by filtration, rinsed with pentane and dried to yield thedesired compound (610 mg, 69%). NMR results confirmed the presence of1,3-bis(3,5-dimethylphenyl)-2-ethoxy-2,3-dihydro-1H-imidazo[4,5-b]pyrazine:¹H NMR (400 MHz, CDCl₃, δ) 1.09 (t, 3H), 2.38 (s, 12H), 3.33 (q, 2H),6.83 (s, 2H), 7.18 (s, 1H), 7.51 (s, 2H), 7.62 (s, 4H).

Synthesis of Compound 2: [(PzI-3,5Me)₂Cu]PF₆

The1,3-bis(3,5-dimethylphenyl)-2-ethoxy-2,3-dihydro-1H-imidazo[4,5-b]pyrazine(400 mg, 1.07 mmol) from step 2, was mixed with [Cu(CH₃CN)₄]PF₆ (199.4mg, 0.535 mmol) and 30 ml of anhydrous THF in a 50 ml flask under N₂atmosphere and refluxed overnight. The resulting bright-yellowsuspension was filtered, the solid was collected, rinsed with THF anddried in vacuo to yield compound 2 (384 mg, 83%). NMR results confirmedthe presence of compound 2: ¹H NMR (400 MHz, acetone-d₆, δ) 2.42 (s,24H), 7.27 (s, 4H), 7.54 (s, 8H), 8.65 (s, 4H).

Synthesis of Compound 3 Step 1: Synthesis ofHydroxy[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ilidene]copper(I)(IPr)CuOH

Synthesized following published procedure (Fortman et al.,Organometallics, 2010, 29, 3966-3972).

Step 2: Synthesis of Compound 3: (IPr)Cu(BzI-3,5Me)BF₄

1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-3-ium tetrafluoroborate(106 mg, 0.26 mmol) and (IPr)CuOH (120 mg, 0.26 mmol) from step 1 weremixed in 20 ml of dry THF and stirred overnight at 60° C. under nitrogenatmosphere. The reaction mixture was cooled to room temperature (˜22°C.) and concentrated to ˜2 ml by rotary evaporation. The product wasprecipitated as the white solid upon addition of ethyl ether (169 mg,76%). NMR results confirmed the presence of compound 3: ¹H NMR (400 MHz,CDCl₃, δ) 0.95 (d, 12H), 1.14 (d, 12H), 2.35-2.42 (m, 16H), 6.68 (s,4H), 6.95 (m, 2H), 7.12-7.17 (m, 8H), 7.27 (m, 2H), 7.42 (t, 2H).

Synthesis of Compound 4 Synthesis of Compound 4: (BzI-3,5Me)CuCl

1,3-bis(3,5-dimethylphenyl)-1H-benzo[d]imidazol-3-ium chloride (500 mg,1.38 mmol), CuCl (164 mg, 1.66 mmol), and NaOtBu (132.5 mg, 1.38 mmol)were mixed with 40 ml of THF and stirred at room temperature overnight.The reaction mixture was then filtered under inert atmosphere through aplug of Celite® and the solvent was evaporated in vacuo. The resultingsolid was exposed to air and washed with pentane (50 ml). The productwas obtained as white air stable solid (466 mg, 79%). NMP resultsconfirmed the presence of compound 4: ¹H NMR (500 MHz, acetone-d₆, δ)2.45 (s, 12H), 7.27 (s, 2H), 7.48 (s, 4H), 7.50-7.52 (m, 2H), 7.61-7.63(m, 2H).

Synthesis of Compound 5 Synthesis of Compound 5: (BzICy)CuCl

1,3-dicyclohexyl-1H-benzo[d]imidazol-3-ium chloride (239.2 mg, 0.75mmol), CuCl (74.2 mg, 0.75 mmol), and NaOtBu (72.1 mg, 0.75 mmol) weremixed with 10 ml of THF and stirred overnight at room temperature undera nitrogen atmosphere. The reaction mixture was then filtered underinert atmosphere through a plug of Celite® and the solvent was removedby rotary evaporation. The product was obtained as white solid. (190 mg,66%). NMR results confirmed the presence of compound 5: ¹H NMR (400 MHz,CDCl₃, δ) 1.38-1.57 (m, 6H), 1.81 (d, 2H), 2.00 (d, 4H), 2.09 (d, 4H),2.43 (qd, 4H), 4.50 (tt, 2H), 7.33-7.36 (m, 2H), 7.55-7.57 (m, 2H).

Synthesis of Compound 6 Synthesis of Compound 6 (PzI-3,5Me)CuCl

1,3-bis(3,5-dimethylphenyl)-2-ethoxy-2,3-dihydro-1H-imidazo[4,5-b]pyrazine(300 mg, 0.8 mmol) and CuCl (72.3 mg, 0.73 mmol) were refluxed overnightin 20 ml of anhydrous THF under N₂ atmosphere. The resultingbright-yellow suspension was filtered, the solid was collected, rinsedwith THF, and dried in vacuo (273 mg, 87%). NMR results confirmed thepresence of compound 6: ¹H NMR (500 MHz, CDCl₃, δ) 2.46 (s, 12H), 7.21(s, 2H), 7.45 (s, 4H), 8.55 (s, 2H).

Synthesis of Compound 7 Synthesis of Compound 7: (PzI-3,5Me)CuBr

1,3-bis(3,5-dimethylphenyl)-2-ethoxy-2,3-dihydro-1H-imidazo[4,5-b]pyrazine(500 mg, 1.335 mmol) and CuBr (174 mg, 1.213 mmol) were refluxedovernight in 30 ml of anhydrous THF under N₂ atmosphere. The resultingbright-yellow suspension was filtered, the solid was collected, rinsedwith THF, and dried in vacuo (407 mg, 71%). NMR results confirmed thepresence of compound 7: ¹H NMR (400 MHz, CDCl₃, δ) 2.46 (s, 12H), 7.20(s, 2H), 7.49 (s, 4H), 8.56 (s, 2H).

Synthesis of Compound 8 Synthesis of Compound 8 (PzI-3,5Me)CuI

1,3-bis(3,5-dimethylphenyl)-2-ethoxy-2,3-dihydro-1H-imidazo[4,5-b]pyrazine(500 mg, 1.335 mmol) and CuI (231 mg, 1.213 mmol) were refluxedovernight in 30 ml of anhydrous THF under N₂ atmosphere. The resultingbright-yellow suspension was filtered, the solid was collected, rinsedwith THF, and dried in vacuo. The solid was then redissolved in 120 mlof CH₂Cl₂ and an insoluble residue was filtered off to give clear yellowsolution, which was concentrated by rotary evaporation to ˜30 ml. Theyellow product precipitated overnight after the addition of diethylether (40 mg, 6%). NMR data confirmed the presence of compound 8: ¹H NMR(400 MHz, CDCl₃, δ) 2.46 (s, 12H), 7.19 (s, 2H), 7.55 (s, 4H), 8.56 (s,2H).

Synthesis of Compound 9 Synthesis of Compound 9: (IPr)Cu(Cbz)

Carbazole (83.6 mg, 0.5 mmol) and NaH (12 mg, 0.5 mmol) were mixed with15 ml of THF and stirred at room temperature under nitrogen atmosphereuntil bubbling stopped (15 min).Chloro[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]copper(I)((IPr)CuCl) (243.8 mg, 0.5 mmol) was added and the reaction mixture wasstirred for 1 hour. The mixture was then filtered under an inertatmosphere through a plug of Celite® and the solvent was removed byrotary evaporation. The product was obtained as white solid (170 mg,55%). NMR results confirmed the presence of compound 9: ¹H NMR (400 MHz,acetone-d₆, δ) 1.31 (d, 24H), 2.82 (sept, 4H), 6.34 (d, 2H), 6.75 (t,2H), 6.87 (t, 2H), 7.55 (d, 4H), 7.73 (t, 2H), 7.80 (d, 2H), 7.87 (s,2H).

Synthesis of Compound 10 Synthesis of Compound 10: (BzICy)Cu(Cbz)

Chloro[1,3-dicyclohexylbenzimidazol-2-ylidene]copper(I) (60 mg, 0.16mmol) and sodium carbazole (30.3 mg, 0.16 mmol) were stirred in 15 ml ofTHF for 1 h at room temperature under nitrogen atmosphere. The reactionmixture was filtered under inert atmosphere through a plug of Celite®and the solvent was removed by rotary evaporation. The product wasobtained as light-yellow solid (45 mg, 51%). NMR results confirmed thepresence of compound 10: ¹H NMR (400 MHz, acetone-d₆, δ) 1.35-1.46 (m,2H), 1.60-1.81 (m, 6H), 2.00 (d, 4H), 2.30 (d, 4H), 2.65-2.80 (m, 4H),4.95 (tt, 2H), 6.96 (t, 2H), 7.25 (t, 2H), 7.45-7.48 (m, 2H), 7.67 (d,2H), 7.93-7.95 (m, 2H), 8.04 (d, 2H).

Compound Data

The photophysical properties of compounds 1-10 were evaluated in thesolid state. The maximum wavelength, the lifetime, and the quantum yieldof compounds 1-10 is summarized in Table 1, below.

TABLE 1 Photophysical properties in the solid state. Compound λ_(max,)(nm) τ QY Compound 1: 462 11.8 μs 0.79 (BzI-3,5Me)₂Cu⁺ Compound 2: 6000.67 μs (26%) <0.01 [(PzI-3,5Me)₂Cu]PF₆ 2.14 μs (73%) Compound 3: 390 —<0.01 (IPr)Cu(BzI-3,5Me)BF₄ Compound 4: 586 2.8 μs (11%) 0.23(BzI-3,5Me)CuCl 10.4 μs (89%) Compound 5: 495 1.3 μs (14%) 0.38(BzICy)CuCl 9.0 μs (86%) Compound 6: 546 4.2 μs 0.26 (PzI-3,5Me)CuClCompound 7: 524 0.39 μs (31%) 0.10 (PzI-3,5Me)CuBr 1.77 μs (69%)Compound 8: 575 — <0.01 (PzI-3,5Me)CuI Compound 9: 414, 435 1.7 ns (16%)0.06 (IPr)Cu(Cbz) 13.5 ns (84%) Compound 10: 530 4.0 μs (16%)(BzICy)Cu(Cbz) 14.5 μs (84%) 0.035

FIG. 4 shows the normalized intensity (A.U.) versus wavelength data forcompounds 1 & 4-7, while FIG. 5 shows the normalized intensity (A.U)versus wavelength data for compounds 9 & 10.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

We claim:
 1. A compound comprising a structure according to formula (I):

wherein C* is a carbene carbon, X₁ is bonded to C* by a C atom, and X₂is bonded to C* by a N atom, and X₁ and X₂ join to form a ring; X₁ isselected from the group consisting of alkyl, cycloalkyl, alkoxy,alkenyl, aryl, heteroalkyl, and heteroaryl; and X₂ is selected from thegroup consisting of heteroalkyl, heteroalkenyl, and heteroaryl; and Y isselected from the group consisting of halide, alkyl, cycloalkyl,alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroalkyl, and heteroaryl.2. The compound of claim 1, wherein Y includes a carbene carbon that iscoordinated to the Cu atom.
 3. The compound of claim 1, wherein the ringformed from X₁ and X₂ is part of a polycyclic ring system.
 4. Thecompound of claim 1, wherein Cu—Y comprises a structure selected fromthe group consisting of:

wherein R is selected from the group consisting of hydrogen, alkyl,cycloalkyl, alkoxy, amino, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, heteroalkynyl, arylalkyl, aryloxy, aryl, heteroalkyl, andheteroaryl.
 5. The compound of claim 1, wherein Cu—Y comprises astructure selected from the group consisting of:

wherein R₁ and R₂ are independently selected from the group consistingof alkyl, cycloalkyl, alkoxy, amino, alkenyl, cycloalkenyl,heteroalkenyl, arylalkyl, aryloxy, aryl, heteroalkyl, and heteroaryl. 6.The compound of claim 1, wherein Y is selected from the group consistingof aryl, heteroalkyl, and heteroaryl.
 7. The compound of claim 1selected from the group consisting of:

wherein z is 1, 2, or 3; wherein R, R₁, R₂, and R₃, are eachindependently selected from the group consisting of hydrogen, alkyl,cycloalkyl, alkoxy, amino, alkenyl, cycloalkenyl, heteroalkenyl,arylalkyl, aryloxy, aryl, heteroalkyl, and heteroaryl.
 8. The compoundof claim 7, wherein Yin formula (I) is selected from the groupconsisting of aryl, heteroalkyl, and heteroaryl.
 9. A consumer productincluding a display, the display including an organic light emittingdevice comprising an anode, a cathode, and an organic layer disposedbetween the anode and the cathode, the organic layer comprising acompound of claim 1 and a host.
 10. The product of claim 9 selected fromthe group consisting of flat panel displays, computer monitors, medicalmonitors, televisions, billboards, lights for interior or exteriorillumination and/or signaling, heads up displays, fully transparentdisplays, flexible displays, laser printers, telephones, cell phones,personal digital assistants (PDAs), laptop computers, digital cameras,camcorders, viewfinders, micro-displays, 3-D displays, vehicles, a wall,theater or stadium screen, and a sign.
 11. An organic light emittingdevice that includes an anode, a cathode, and an organic layer disposedbetween the anode and the cathode, wherein the organic layer is anemissive layer that comprises a compound of claim 1 and a host, thecompound being an emissive dopant.
 12. An organic light emitting devicethat includes an anode, a cathode, and an organic layer disposed betweenthe anode and the cathode, wherein the organic layer comprises acompound of claim 1 and a host, the compound being a non-emissivedopant.
 13. The device of claim 11, wherein the host comprises at leastone chemical group selected from the group consisting of triphenylene,carbazole, dibenzothiphene, dibenzofuran, dibenzoselenophene,azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, andaza-dibenzoselenophene.
 14. The device of claim 11, wherein the host isa compound selected from the group consisting of:

and combinations thereof.
 15. An organic light emitting devicecomprising an anode, a cathode, and an organic layer disposed betweenthe anode and the cathode, the organic layer comprising a compound ofclaim 7 and a host, wherein the organic layer is an emissive layer.